The present invention relates generally to threaded fasteners of any size, and more particularly to vibration resistant threaded fasteners.
Threaded fasteners such as screws are used in many applications to connect one component or part to another. Many screws are installed through a portion of one component and threaded into a second component to clamp the components together. Many component shapes and configurations have been contemplated for retaining a threaded fastener, such as a blind or through hole formed in the component for engaging the threads of the fastener. The blind or through hole may be provided in an embossment or may be provided in the component material thickness. Often the blind or through hole is threaded to mate with the threaded fastener.
Many applications including automotive, electronic, and consumer products require threaded fasteners that maintain desired clamping forces through vibration and other in-use loads. A common problem with prior fasteners included loosening under vibration. Other prior fasteners stripped too easily during installation providing reduced clamping and premature assembly failure. Certain prior fasteners create excessive radial stress around the hole during installation, particularly in an embossment, that weakens the component and may cause premature assembly failure.
Fastener coatings have been developed to compensate for some of the failures of prior fasteners, such as thread-sealing adhesives, thread lubricants, anti-vibration coatings, and patches of nylon or similar materials. However, thread coatings require additional material cost and application cost, and are increasingly difficult to apply as fastener sizes become smaller. There remains a need for a threaded fastener that overcomes these and other disadvantages of the prior art.
We have found that new thread profiles that provide multi-point contact improve the vibration resistance of the threaded fastener, and thereby greatly reduce and may eliminate the need for fastener coatings, such as nylon patches.
Therefore, what is disclosed is a threaded fastener with improved vibration resistance. The threaded fastener includes a first end, a second end, and a threaded portion extending between the first end and the second end. The threaded fastener also has a longitudinal axis extending through the fastener from the first end to the second end, and a normal axis extending perpendicular to the longitudinal axis.
In various embodiments, the threaded faster has a threaded portion configured to engage two or three points of a mating thread, and the threaded portion has a thread defined by, in series, a crest portion oriented at an angle of 10° to 20° relative to the longitudinal axis, a leading flank oriented at an angle of 20° to 30° relative to the normal axis, a root portion oriented at an angle of 25° to 35° relative to the longitudinal axis, and a trailing flank oriented at angle of 15° to 25° relative to the normal axis.
In one embodiment, the threaded fastener has a threaded portion configured to engage three points of a mating thread, and the threaded portion has a thread defined by, in series, a crest portion oriented at an angle of −5° to 5° relative to the longitudinal axis, a leading flank oriented at an angle of 30° to 40° relative to the normal axis, a root portion oriented at an angle of 22° to 32° relative to the longitudinal axis, and a trailing flank oriented at angle of 17° to 27° relative to the normal axis. In other embodiments, the thread is defined by, in series, the crest portion oriented at an angle of approximately 0° relative to the longitudinal axis, the leading flank oriented at an angle of approximately 35° relative to the normal axis, the root portion oriented at an angle of approximately 27° relative to the longitudinal axis, and the trailing flank oriented at an angle of approximately 22° relative to the normal axis. In yet other embodiments, the crest portion, the leading flank, the root portion, and the trailing flank may be oriented at +/−1° or +/−2.5° from the angles previously noted.
In another embodiment, the threaded fastener has a threaded portion configured to engage two points of a mating thread, and the threaded portion has a thread defined by, in series, a crest portion oriented at an angle of 10° to 20° relative to the longitudinal axis, a leading flank oriented at an angle of 20° to 30° relative to the normal axis, a root portion oriented at an angle of 25° to 35° relative to the longitudinal axis, and a trailing flank oriented at an angle of 15° to 25° relative to the normal axis. In other embodiments, the thread is defined by, in series, the crest portion oriented at an angle of approximately 15° relative to the longitudinal axis, the leading flank oriented at an angle of approximately 25° relative to the normal axis, the root portion oriented at an angle of approximately 30° relative to the longitudinal axis, and the trailing flank oriented at angle of approximately 20° relative to the normal axis. In yet other embodiments, the crest portion, the leading flank, the root portion, and the trailing flank may be oriented at +/−1° or +/−2.5° from the angles previously noted.
In another embodiment, the threaded fastener has a threaded portion configured to engage two points of a mating thread, and the threaded portion has a thread defined by, in series, a crest portion oriented at an angle of −5° to 5° relative to the longitudinal axis, a leading flank oriented at an angle of 25° to 35° relative to the normal axis, a first root portion oriented at an angle of −5° to 5° relative to the longitudinal axis, a second root portion oriented at an angle of 35° to 45° relative to the longitudinal axis, and a trailing flank oriented at angle of 21° to 29° relative to the normal axis. In other embodiments, the thread is defined by, in series, the crest portion oriented at an angle of approximately 0° relative to the longitudinal axis, the leading flank oriented at an angle of approximately 30° relative to the normal axis, the first root portion oriented at an angle of approximately 0° relative to the longitudinal axis, the second root portion oriented at an angle of approximately 40° relative to the longitudinal axis, and the trailing flank oriented at angle of approximately 24° relative to the normal axis. In yet other embodiments, the crest portion, the leading flank, the root portion, and the trailing flank may be oriented at +/−1° or +/−2.5° from the angles previously noted.
In some embodiments, the second end of the threaded fastener is tapered. In an embodiment, the major diameter of the crest portion of the threaded portion tapers at approximately 30° over at least the last two revolutions of the threaded portion adjacent the second end.
The presently disclosed threaded fastener may be internally or externally threaded. In addition, the threaded fastener may include internal or external driver surfaces. In one embodiment the threaded fastener has a recess into a shank which defines internal drive surfaces. In yet other embodiments, the threaded fastener includes a radially extending surface with a plurality of serrations.